Reversing rudders



Mar. 27, 1923.

REVERSING RUD-DERS FILED JUNE 30' I922.

fare/76hr JRAJexa/ma- J. R. ALEXANDER.- 1 4 3- JOHNSTON ROBERTSON ALEXANDER, OF LIVEEPOOL, ENGLAND, ASSIG-NOE TO JOHN GEORGE AULSEBBOOK KITCHEN, OF LANCASTER, ENGLAND,.GORDON HENRY FRASER AND JAMES RYDER OHANLON, BOTH 0F LIVERPOOL, ENGLAND.

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Application filed June 30, 1922. SeriaI No. 571,909.

T 0 all whom it may concern:

Be it known that I, JOHNSTON ROBERTSON ALnxANnnR, a subject of the King of Great Britain and Ireland, and resident of Liverpool, England, have invented certain new and useful Improvements Relating to Reversing Rudders, of which the following is a specification.

This invention relates to duplex rudders for ships and the like which are adapted to be moved through equal angles in the same or in opposite directions for the purposes of steering, speed variation and reversing. With such rudders the magnitude of the twisting moments developed and transmitted to the rudder stocks both when steering and the ship travelling ahead and when closing the rudder blades to reverse the motion of the ship depends on the proportions of the rudder blades which are forward and aft of the axis of rotation thereof.

The object of the present invention is to reduce the twisting moments developed and transmitted to the rudder stoc rs in all or any positions to which the rudder blades may be turned, thereby reducing the effort required to operate the rudders whether for steering or for speed variation and reversing purposes.

My invention comprises the combination with duplex rudder blades, of short or narrow supplementary vanes. one of which is.

disposed within and at a distance from each main blade and positioned forward of its axis of rotation, the said vanes when the rudder blades are being moved to close behind the propeller, swinging just clear of and immediately behind the tips of the latter so that an intense pressure is imposed thereon due to the impingement and Cl8fi(1 tion of the propeller stream, which results in a turning moment which tends to close the rudders.

My invention further comprises the formation of the main'rudder blades with aminimum area forward of their axis of rotation, the short supplementary vanes being within this area.

Referring to the" accompanying sheet of explanatory drawings Figure 1 is an elevation and Figure 2 a sectional plan view of duplex rudders constructed and arranged in accordance with this invention.

Figure 3 is a sectional plan view showing the rudders in their closed positions.

The same reference letters in the three views indicate the same parts.

The rudder blades (1, b which may be of curved or flat form adapted when closed behind the propeller as shown in Figure 3 to provide a pocket which reverses the stream from the propeller, have therein short or narrow supplementary vanes 0, d which may be of similar shape to the rudder blades. They may be axially parallel to the. main blades as shown or inclined thereto in either direction. The area of the main blades (1, b which lies forward of their axis of rotation is reduced to a minimum so as to reduce to a desired minimum the magnitude of the twisting moments upon the rudder stocks when the rudders are being turned in the same angular direction for steering ahead. By reducing the said area forward of the rudder axis, 1 increase the magnitude of the twisting moments upon the rudder stocks when the rudders are being moved to close behind the propeller for reversing purposes, but the short supplementary disposition and proportions, as hereinafter more fully described, compensate for the said reduction in area and facilitate the ready closure of the rudders.

Relatively to each main rudder blade, the short supplementary vanes lie wholly forward of the axis of rotation. Radially the short vanes are disposed to swing or move just clear of the tips of the propeller 6. When so swung or moved for speed variation or reversing purposes, they pass immediately behind the tips of the propeller as shown in Figure 3 so that they receive an intense pressure due to the impingement and deflection of the propeller stream. The 'di rection of this pressure is normal or approximately normal to the surface of the short vanes and result-s therefore in a turning moment which tends to close the rudder blades.

It will be understood that 7 indicates the I portions of the rudder blades which are aft of the axis of rotation and g the portions which are forward thereof.

I do not limit myself to any particular details of the method of securing the short supplementary vanes in place,-but may vary vanes 0, d by reason of their the same to suit the forms of rudder plates and any other particular requirements.

I claim 1. In reversing rudders, the combination with duplex rudder blades of a short or narrow supplementary vane secured thereto within and spaced a short distance from each of said blades and forward of its axis of rotation. as set forth.

2. In reversing rudders, in combination,

duplex rudder blades having but a small portion of their area forward of their axis of rotation, a. short or narrow supplementary vane secured thereto Within and spaced at a short distance from each of said blades and forward of its axis of rotation, as set forth.

In testimony whereof I have signed my name to this specification.

JOHNSTON ROBERTSON ALEXANDER. 

